Synthesis and characterization of multiferroic BiMn7_7O12_{12}

We report on the high pressure synthesis of BiMn$_7$O$_{12}$, a manganite displaying a "quadruple perovskite" structure. Structural characterization of single crystal samples shows a distorted and asymmetrical coordination around the Bi atom, due to presence of the $6s^{2}$ lone pair, resulting in non-centrosymmetric space group Im, leading to a permanent electrical dipole moment and ferroelectric properties. On the other hand, magnetic characterization reveals antiferromagnetic transitions, in agreement with the isostructural compounds, thus evidencing two intrinsic properties that make BiMn$_7$O$_{12}$ a promising multiferroic material.Comment: 4 pages, 3 figure

Crystallographic disorder and electron scattering on structural two-level systems in ZrAs1.4Se0.5

Single crystals of ZrAs1.4Se0.5 (PbFCl type structure) were grown by chemical vapour transport. While their thermodynamic and transport properties are typical for ordinary metals, the electrical resistivity exhibits a shallow minimum at low temperatures. Application of strong magnetic fields does not influence this anomaly. The minimum of the resistivity in ZrAs1.4Se0.5 apparently originates from interaction between the conduction electrons and structural two-level systems. Significant disorder in the As-Se substructure is inferred from X-ray diffraction and electron microprobe studies

1-(4-Bromo-3-chloro­phen­yl)-3-meth­oxy-3-methyl­urea (chlorbromuron)

In the title urea-based herbicide, C9H10BrClN2O2, there exist multiple inter- and intra­molecular inter­actions. Most notably, the intra­molecular hydrogen bond between the urea carbonyl O atom and an aromatic H atom affects the planarity and torsion angles of the mol­ecule by restricting rotations about the Ar—secondary amine N and the secondary amine N and the carbonyl C. The two N atoms in the urea fragment are in different environments. One is planar; the other, pseudo-C 3v. It is likely that the different nitro­gen-atom geometries and the restricted rotations within the mol­ecule impact the bioactivity of chlorbromuron

Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}

Electrical resistivity $\rho$, specific heat C, and magnetic susceptibility $\chi$ measurements made on the filled skutterudite CeRu_4As_{12} reveal non-Fermi liquid (NFL) T - dependences at low T, i.e., $\rho$(T) $\sim$ T^{1.4} and weak power law or logarithmic divergences in C(T)/T and $\chi$(T). Measurements also show that the T - dependence of the thermoelectric power S(T) deviates from that seen in other Ce systems. The NFL behavior appears to be associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than a typical Kondo lattice scenario that would be appropriate for an integral Ce valence of 3^+.Comment: 18 pages, 5 figure

NaV2O4: a Quasi-1D Metallic Antiferromagnet with Half-Metallic Chains

NaV2O4 crystals were grown under high pressure using a NaCl flux, and the crystals were characterized with X-ray diffraction, electrical resistivity, heat capacity, and magnetization. The structure of NaV2O4 consists of double chains of edge-sharing VO6 octahedra. The resistivity is highly anisotropic, with the resistivity perpendicular to the chains more than 20 times greater than that parallel to the chains. Magnetically, the intrachain interactions are ferromagnetic and the interchain interactions are antiferromagnetic; 3D antiferromagnetic order is established at 140 K. First principles electronic structure calculations indicate that the chains are half metallic. Interestingly, the case of NaV2O4 seems to be a quasi-1D analogue of what was found for half-metallic materials.Comment: 14 pages, including 4 figures and 1 table, accepted for publication in PR

Synthesis and crystal structure of N-6-[(4-pyridylamino) carbonyl]-pyridine-2-carboxylic acid methyl ester zinc complex

A reaction between monoamide ligand namely N-6-[(4-pyridylamino)carbonyl]-pyridine-2-carboxylic acid methyl ester (L4) and zinc chloride has been attempted in order to generate a carboxylate complex suitable for anion inclusion. This reaction gives rise to a formation of discrete complex with general formula [ZnCl2(L4)2]. Complex [ZnCl2(L4)2] crystallizes in the monoclinic space group, P21/c, with one zinc(II) center, one molecule of ligand L4, one coordinated chloride and one methanol molecule in the asymmetric unit. The extended structure of this molecule shows that the zinc atom is coordinated by four donors: two L4 and two chloride anions. The zinc atom adopts distorted tetrahedral geometry with the angles between the donors in the range 103.62(11)-122.74(8)°. In this study, the amide cavity is bound with methanol through hydrogen-bonding interactions. The methanol molecules is hydrogen bonded to the amide moiety with bond lengths O30-H8···O12 and N17-H17···O30 of 1.988 and 2.078 Å, respectively

cis-Bis[4-amino-N-(pyrimidin-2-yl)benzene­sulfonamido-κ2 N,N′]bis­(dimethyl sulfoxide-κO)cadmium

The complete mol­ecule of the title compound, [Cd(C10H9N4O2S)2(C2H6OS)2], is completed by the application of a twofold rotation axis. The CdII atom is six coordinated by two bidentate sulfadiazinate anions and two dimethyl­sulfoxide mol­ecules. The resulting N4O2 donor set displays a distorted trigonal–prismatic coordination geometry. The S atom and methyl groups of dimethyl­sulfoxide are disordered over two sets of sites, with site occupancies of 0.715 (4) and 0.285 (4). The crystal structure features inter­molecular N—H⋯N and N—H⋯O hydrogen bonds that lead to the formation of layers in the ab plane

The structure of aliphatic amine adducts of uranyl acetylacetonate. I. Dioxobis(2,4-pentanedionato)mono (2-N-methylaminopentan-4-one)uranium(VI)

Crystals of the title compound are monoclinic with a= 8.314 (5), b= 22.723 (9), c= 12.589 (6) A, /3= 123.0 (2t, Z=4, space group P2dc. The structure was determined by Patterson and Fourier methods and refined by full-matrix least squares to a final R of 0.030 for 2043 independent reflexions. The U atom has pentagonal bipyramidal coordination and the N-methylacetylacetoneamine is bonded to U via O. There are two intramolecular N-H. . .0 hydrogen bonds which govern the geometry of the adduct molecule